Analysis of fractures yields improved gas production from Zechstein carbonates, Hewett Field, UKCS

The Hewett Field complex, discovered twenty seven years ago, is located in the south-west of the Southern North Sea Basin (United Kingdom sector). Gas is currently being produced from four separate reservoirs: Upper and Lower Bunter sandstones as well as Rotliegendes sandstones and Zechstein dolomites (Fig. 1). Figure 2 is a generalized stratigraphic section for the south-west part of the basin. The Zechstein is a sequence of carbonate and evaporitic rocks of late Permian age, which underlies a considerable area of north-west Europe. In places, five cycles can be identified: Z1 to Z5. A typical cycle reflects the influence of increasing salinity through evaporation following an initial marine incursion.